It is still too early into the investigation of yesterday’s dual bombings along the route of the Boston Marathon to know for sure what actual explosives were used in the attack. Having said that a CNN report yesterday makes the following comment:
“Based on the bombs' effects, the devices could have been small enough to be concealed in small bags or boxes, a law enforcement official said. The smoke was consistent with a "low-velocity improvised explosive mixture, perhaps flash powder or sugar chlorate mixture," the official said.”
IF the ‘sugar chlorate’ mixture was the material of construction, it MIGHT indicate (note the big ‘IF’ and the big ‘MIGHT”, this is all speculation at this point) it might indicate that a theft/diversion of a DHS chemical of interest (COI) was involved in this attack. Either sodium chlorate or potassium chlorate would be effective in this role and both are DHS COI.
The theft/diversion would not necessarily have had to come from a CFATS covered facility. The small size of the device (probably less than 1.5 gallons according to the previously mentioned news story) would have required must less than the 400 lbs Screening Threshold Quantity (STQ) that would initiate the CFATS coverage process.
If it turns out that one of those two chlorates was actually used in the bombs (and the FBI labs will certainly be able to determine that), then we can be pretty sure that FBI agents will be visiting all CFATS facilities in the Northeast (and probably everywhere east of the Rockies) that reported inventories of either of the two components on their Top Screens. I would assume that ISCD would share that data with the FBI on all top screen submissions, not just currently covered facilities.
We’ll just have to follow the news and see where this takes us.